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Calculated beam quality correction factors for ionization chambers in MV photon beams
J Tikkanen1, K Zink, M Pimpinella
1Radiation and Nuclear Safety Authority (STUK), Helsinki, Finland. Helsinki Institute of Physics, University of Helsinki, Helsinki, Finland.
Physics in Medicine and Biology
|January 30, 2020
Summary
This study calculated beam quality correction factors for 10 ionization chamber models in linear accelerator beams. Results show good agreement between partners and literature, with differences noted compared to TRS-398 data.
Area of Science:
- Medical Physics
- Radiation Oncology Dosimetry
Background:
- The beam quality correction factor (kQ) is crucial for accurate radiation therapy dosimetry.
- Uncertainty in kQ is a major contributor to dose determination uncertainty.
Purpose of the Study:
- To improve the accuracy of available kQ data.
- To calculate kQ factors for 10 ionization chamber models across a range of linear accelerator beam qualities (6-25 MV), including flattening-filter-free (FFF) beams.
Main Methods:
- Utilized EGSnrc and PENELOPE software for Monte Carlo simulations.
- Incorporated ICRU Report 90 cross-section data for water and graphite.
- Calculated volume averaging correction factors for ionization chamber cavities.
Main Results:
- Achieved good agreement between calculation partners and with existing literature.
- Observed that kQ values from TRS-398 were generally higher than the calculated values.
- Found that kQ values for FFF beams did not consistently follow the same trends as flattened beams.
Conclusions:
- The study provides a valuable dataset for kQ factors, enhancing radiation therapy dosimetry accuracy.
- Discrepancies with TRS-398 and unique behavior of FFF beams highlight areas for further investigation.
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